Decolorizing process



ne '10 1 24 v 1,497,13

E. S. FARROW, JR., ET AL DECOLORIZING PROCES S Filed March 7, 1923 IN V EN TOR.

' A TTORNEY Patented June 10, 1924.

UNITED STATES 1,497,138 PATENT OFFICE.

EDWARD'S. FARBOW, JR., AND NEIL S. KOCHER, OF ROCHESTER, NEW YORK, AS- SIGNORS TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YO'RK, A CORPORA- TION or NEW YORK.

' DECOLORIZING rnocnss. f

' Application filed March 7, 1923. Serial No. 623,340. A

To all whom it may concern:

Be it known that we, EDWARD S. FARROW, Jr., and NEIL S. KocHER. citizens of the United States of America, residing at Rochester, iu the county of Monroe and State of New York, have invented certain new and useful Improvements in Decolorizing Processes, of which the following is a full, clear, and exact specification.

This invention relates to a process for removing dye from colored materialby means of a liquid and then removing the dye from the liquid. One object of the invention is to provide a process for removing dye from colored material, such as tinted or colored cellulosic films, economically, reliably and rapidly, even when done on a large scale.

Other objects-will hereinafter appear.

In the accompanying drawing the single fignre is a diagrammatic sectional view of an apparatus in which our process may conveniently be carried out.

Since our invention is particularly applicable to the removal of dye from tinted cellulosic bases or supports of photographic film, the embodiment which will be described by way of illustration, will be particularly directed to such film, but the invention is, 0 course, not limited to this particular field. Photographic films have come into extensive use, the bases or supports of which contain a colored or dyed layer. The latter is usually, but not necessarily, on the rear side of the support. During the process of manufacture this. colored layer sometimes becomes too deep in tint. It is then desirable to reduce the color without dissolving or in any way impairing the base or support, the decolorizing action being under control, so as to be stopped at the right point. Moreover scrap or other waste pieces of such film or film base often accumulate and it is desirable to remove the color entirely from them before they are utilized, this removal being eifected without dissolving them.

We have discovered that these conditions can be met by removing the dye wholly or partially, as the requirements may dictate, by means of a suitable liquid and then separating the liquid from the material and treating it with decolorizing material. As a suitable liquid we prefer one which has a temporary softening action on the film without dissolving the latter, yet has a solvent action with respect to the dye. The softenmg effect permits the liquid to get into suitable contact with the dye. One of the best ways of effecting this result is to mix a substance which by itself would be a solvent of the cellulosefilm and a substance which is a non-solvent of said film, at least one of the substances being a solvent of the dye to be removed. The percentage of film solvent in the mixture isalways kept below the amount which might dissolve the film; in other words, the non-solvent is suflicient to transform the solvent tendency of the other ingredient into a slight softening action. Our process is particularly adapted to the standard nitrocellulose colored motion picture positive film, but is also useful in connection with cellulose acetate and cellulose ether.

films, these being typical examples of such cellulosic materials.

By way of illustration, we prepare a bath useful with respect to all of the above mentioned films, but especially with respect to nitrocellulose films by mixing 30 parts of acetone with 70 parts of water. suiiicient'ly rapidly at ordinary temperatures withoutthe need of heating to accelerate it,

conditions seem to make it advisable. The film to be treated is agitated in connection with this bath, preferably in the cut up or subdivided state, the bath being then drawn 01f and the color removed from it separately by contacting it with a decolorizing carbon like bone-char.

For example, we may place colored film pieces 1, preferably chopped up, in a tank 2 containing a bath of the decolorizing liquid 3, the tank having a perforated or false bottom 4 and agitating blades 5 driven by the rotation of shaft 6. These blades 5 may be inclined, as shown in the drawings, so as to give a vertical component to the movement of the bath and film pieces.

The liquid containing the extracted dye is then run through pipe 7 to a decolorizing station or tower 8. Where the top of the tower is below the level of the tank 2, this flow may be eflected by gravity, but ordinarily it is strongly preferable to provide a pump. 9 for insuring the flow of the liquid under pressure through the apparatus. The liquid in the tower 8 passes'through coarse bone-char 10 supported on a suitable filter This acts f mild heating being permissible, however, if

11, say of felt, carried by a perforated plate. This-plate may be clamped between sections of the tower, said seotionshaving flanges 13, 14: joined by bolts 15. The decolorizing liquid passes from the end of the decolorizmg tower 8 through pipe 16 back into tank 2, the pressure of pump 9 being sutlicient to effect this result. The liquid entering tank 2, being substantially fresh, has a particularly strong dye-removing action on the colored material 1. It will be noted that the process is a cyclic one, the liquid being continuously moved and the film scrap e with freshly revived liquid.

Of course, many equivalent liquids can be prepared in accordance with the principles stated hereinabove. A 15% solution of methyl alcohol in water or in butyl alcohol is mentioned by way of illustration. The apparatus for extracting the dye from the material can, of course, be widely varied ,and other structures than decolorizing towers may be employed for separately acting on the liquid withbone-char, as will be readily understood by those skilled in the art. The process operates satisfactorily on both acid and basic dyes. The theory of the decolorizing action of the carboniferous material appears to be that this material has a Specific attraction for the dye or coloring substance.

. When'the dye is not to be removed entirely but the tint of a film base is to be reduced uniformly, it is not chopped up but is treated in the decolorizing liquid 3, preferably-without its adjacent folds or convolutions touching each other. The film also may be moved continuously through the liquid 3 by any of the well known devices for fluid-treating film.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. The process of removing color from ing always agitated mamas dyed cellulosicmaterial and regenerating the color-removing agent, which comprises treating said material with a dye-removing liquid, separating said liquid from said material, and treating the separated liquid with decolorizing material.

2. The process of removing color from dyed cellulosic material and regenerating the color removing agent, which comprises treating said material with a dye-removing liquid, separating said liquid from said material, and treating the separated liquid with decolorizinp carbon. l

3. The process of removing color from dyed ccllulosic addition compounds and re generating the color removing agent, which comprises treating said compounds with a liquid which has a solvent action on the dye and a softening action on said compounds, separating said liquid from said compounds, and treating the separated liquid with decolorizing material.

4. The process of decolorizing dyed cellulosic film and regenerating the color removing agent, which comprises treating said film with a liquid containing a substance which is a solvent of said film and a substance which is a non-solvent of said film, at least one of said substances being a solvent of the dye, the proportion of film solvent being suliicient to permit penetration of said dye solvent without substantially dissolving said film, separating said liquid from said film, and treating said liquid with decolorizing carbon.

5 The process of decolorizing dyed nitro-v cellulose film and regenerating the color removing agent, which comprises leachingout the dye from the film by a mixture of water and acetone, drawing ofi said mixture. and passing it through decolorizing bone-char.

Signed at Rochester, New York, this 28th day of February, 1923.

EDWARD SFARRUW, Jr.

NEIL S. KOCHER. 

